Irvine's four-year association with Ferrari will draw to a close at the end of the current season, when he makes way for Rubens Barrichello.
The Brazilian was yesterday confirmed as the new No 2 at Maranello. Barrichello will sign a two-year contract which sees him become the new junior partner for Schumacher.
Irvine will now almost certainly take up the vacancy left by Barrichello at Stewart-Ford, who are set to become Jaguar from next season. The 33- year-old will be handed the No 1 role he has craved for so long, with Johnny Herbert retaining his seat in a line-up which will be confirmed after next weekend's Italian Grand Prix at Monza.
"It would have been impossible to stay with Ferrari as No 2 to Michael," said Irvine, who still has the drivers' world title in his sights. "This is the end of a marvellous experience for me. I want to thank Ferrari because they have done as much for me as I've done for them. I made my debut in 1996 with a podium finish and I've now got the chance to win the world title. But all stories have to come to an end."
Irvine lies one point behind the current leader and reigning world champion, Mika Hakkinen, going into the last four races. These are at Monza, the European at the Nurburgring, Malaysia and Japan.
Ferrari thanked Irvine and said they will do all they can to see him become their first champion since Jody Scheckter in 1979. Their statement said, "Both the team and the driver will put all their efforts and determination into tackling the decisive four remaining races."